/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 * 
 *      http://www.apache.org/licenses/LICENSE-2.0
 * 
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.apache.jasper.compiler;

import java.io.CharArrayWriter;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.InputStreamReader;
import java.net.MalformedURLException;
import java.net.URL;
import java.util.List;
import java.util.Vector;
import java.util.jar.JarFile;

import org.apache.jasper.JasperException;
import org.apache.jasper.JspCompilationContext;
import org.apache.juli.logging.Log;
import org.apache.juli.logging.LogFactory;

/**
 * JspReader is an input buffer for the JSP parser. It should allow unlimited
 * lookahead and pushback. It also has a bunch of parsing utility methods for
 * understanding htmlesque thingies.
 * 
 * @author Anil K. Vijendran
 * @author Anselm Baird-Smith
 * @author Harish Prabandham
 * @author Rajiv Mordani
 * @author Mandar Raje
 * @author Danno Ferrin
 * @author Kin-man Chung
 * @author Shawn Bayern
 * @author Mark Roth
 */

class JspReader {

	/**
	 * Logger.
	 */
	private Log log = LogFactory.getLog(JspReader.class);

	/**
	 * The current spot in the file.
	 */
	private Mark current;

	/**
	 * What is this?
	 */
	private String master;

	/**
	 * The list of source files.
	 */
	private List sourceFiles;

	/**
	 * The current file ID (-1 indicates an error or no file).
	 */
	private int currFileId;

	/**
	 * Seems redundant.
	 */
	private int size;

	/**
	 * The compilation context.
	 */
	private JspCompilationContext context;

	/**
	 * The Jasper error dispatcher.
	 */
	private ErrorDispatcher err;

	/**
	 * Set to true when using the JspReader on a single file where we read up to
	 * the end and reset to the beginning many times. (as in
	 * ParserController.figureOutJspDocument()).
	 */
	private boolean singleFile;

	/**
	 * Constructor.
	 * 
	 * @param ctxt
	 *            The compilation context
	 * @param fname
	 *            The file name
	 * @param encoding
	 *            The file encoding
	 * @param jarFile ?
	 * @param err
	 *            The error dispatcher
	 * @throws JasperException
	 *             If a Jasper-internal error occurs
	 * @throws FileNotFoundException
	 *             If the JSP file is not found (or is unreadable)
	 * @throws IOException
	 *             If an IO-level error occurs, e.g. reading the file
	 */
	public JspReader(JspCompilationContext ctxt, String fname, String encoding,
			JarFile jarFile, ErrorDispatcher err) throws JasperException,
			FileNotFoundException, IOException {

		this(ctxt, fname, encoding, JspUtil.getReader(fname, encoding, jarFile,
				ctxt, err), err);
	}

	/**
	 * Constructor: same as above constructor but with initialized reader to the
	 * file given.
	 */
	public JspReader(JspCompilationContext ctxt, String fname, String encoding,
			InputStreamReader reader, ErrorDispatcher err)
			throws JasperException, FileNotFoundException {

		this.context = ctxt;
		this.err = err;
		sourceFiles = new Vector();
		currFileId = 0;
		size = 0;
		singleFile = false;
		pushFile(fname, encoding, reader);
	}

	/**
	 * @return JSP compilation context with which this JspReader is associated
	 */
	JspCompilationContext getJspCompilationContext() {
		return context;
	}

	/**
	 * Returns the file at the given position in the list.
	 * 
	 * @param fileid
	 *            The file position in the list
	 * @return The file at that position, if found, null otherwise
	 */
	String getFile(final int fileid) {
		return (String) sourceFiles.get(fileid);
	}

	/**
	 * Checks if the current file has more input.
	 * 
	 * @return True if more reading is possible
	 * @throws JasperException
	 *             if an error occurs
	 */
	boolean hasMoreInput() throws JasperException {
		if (current.cursor >= current.stream.length) {
			if (singleFile)
				return false;
			while (popFile()) {
				if (current.cursor < current.stream.length)
					return true;
			}
			return false;
		}
		return true;
	}

	int nextChar() throws JasperException {
		if (!hasMoreInput())
			return -1;

		int ch = current.stream[current.cursor];

		current.cursor++;

		if (ch == '\n') {
			current.line++;
			current.col = 0;
		} else {
			current.col++;
		}
		return ch;
	}

	/**
	 * Back up the current cursor by one char, assumes current.cursor > 0, and
	 * that the char to be pushed back is not '\n'.
	 */
	void pushChar() {
		current.cursor--;
		current.col--;
	}

	String getText(Mark start, Mark stop) throws JasperException {
		Mark oldstart = mark();
		reset(start);
		CharArrayWriter caw = new CharArrayWriter();
		while (!stop.equals(mark()))
			caw.write(nextChar());
		caw.close();
		reset(oldstart);
		return caw.toString();
	}

	int peekChar() throws JasperException {
		if (!hasMoreInput())
			return -1;
		return current.stream[current.cursor];
	}

	Mark mark() {
		return new Mark(current);
	}

	void reset(Mark mark) {
		current = new Mark(mark);
	}

	boolean matchesIgnoreCase(String string) throws JasperException {
		Mark mark = mark();
		int ch = 0;
		int i = 0;
		do {
			ch = nextChar();
			if (Character.toLowerCase((char) ch) != string.charAt(i++)) {
				reset(mark);
				return false;
			}
		} while (i < string.length());
		reset(mark);
		return true;
	}

	/**
	 * search the stream for a match to a string
	 * 
	 * @param string
	 *            The string to match
	 * @return <strong>true</strong> is one is found, the current position in
	 *         stream is positioned after the search string, <strong> false</strong>
	 *         otherwise, position in stream unchanged.
	 */
	boolean matches(String string) throws JasperException {
		Mark mark = mark();
		int ch = 0;
		int i = 0;
		do {
			ch = nextChar();
			if (((char) ch) != string.charAt(i++)) {
				reset(mark);
				return false;
			}
		} while (i < string.length());
		return true;
	}

	boolean matchesETag(String tagName) throws JasperException {
		Mark mark = mark();

		if (!matches("</" + tagName))
			return false;
		skipSpaces();
		if (nextChar() == '>')
			return true;

		reset(mark);
		return false;
	}

	boolean matchesETagWithoutLessThan(String tagName) throws JasperException {
		Mark mark = mark();

		if (!matches("/" + tagName))
			return false;
		skipSpaces();
		if (nextChar() == '>')
			return true;

		reset(mark);
		return false;
	}

	/**
	 * Looks ahead to see if there are optional spaces followed by the given
	 * String. If so, true is returned and those spaces and characters are
	 * skipped. If not, false is returned and the position is restored to where
	 * we were before.
	 */
	boolean matchesOptionalSpacesFollowedBy(String s) throws JasperException {
		Mark mark = mark();

		skipSpaces();
		boolean result = matches(s);
		if (!result) {
			reset(mark);
		}

		return result;
	}

	int skipSpaces() throws JasperException {
		int i = 0;
		while (hasMoreInput() && isSpace()) {
			i++;
			nextChar();
		}
		return i;
	}

	/**
	 * Skip until the given string is matched in the stream. When returned, the
	 * context is positioned past the end of the match.
	 * 
	 * @param s
	 *            The String to match.
	 * @return A non-null <code>Mark</code> instance (positioned immediately
	 *         before the search string) if found, <strong>null</strong>
	 *         otherwise.
	 */
	Mark skipUntil(String limit) throws JasperException {
		Mark ret = null;
		int limlen = limit.length();
		int ch;

		skip: for (ret = mark(), ch = nextChar(); ch != -1; ret = mark(), ch = nextChar()) {
			if (ch == limit.charAt(0)) {
				Mark restart = mark();
				for (int i = 1; i < limlen; i++) {
					if (peekChar() == limit.charAt(i))
						nextChar();
					else {
						reset(restart);
						continue skip;
					}
				}
				return ret;
			}
		}
		return null;
	}

	/**
	 * Skip until the given string is matched in the stream, but ignoring chars
	 * initially escaped by a '\'. When returned, the context is positioned past
	 * the end of the match.
	 * 
	 * @param s
	 *            The String to match.
	 * @return A non-null <code>Mark</code> instance (positioned immediately
	 *         before the search string) if found, <strong>null</strong>
	 *         otherwise.
	 */
	Mark skipUntilIgnoreEsc(String limit) throws JasperException {
		Mark ret = null;
		int limlen = limit.length();
		int ch;
		int prev = 'x'; // Doesn't matter

		skip: for (ret = mark(), ch = nextChar(); ch != -1; ret = mark(), prev = ch, ch = nextChar()) {
			if (ch == '\\' && prev == '\\') {
				ch = 0; // Double \ is not an escape char anymore
			} else if (ch == limit.charAt(0) && prev != '\\') {
				for (int i = 1; i < limlen; i++) {
					if (peekChar() == limit.charAt(i))
						nextChar();
					else
						continue skip;
				}
				return ret;
			}
		}
		return null;
	}

	/**
	 * Skip until the given end tag is matched in the stream. When returned, the
	 * context is positioned past the end of the tag.
	 * 
	 * @param tag
	 *            The name of the tag whose ETag (</tag>) to match.
	 * @return A non-null <code>Mark</code> instance (positioned immediately
	 *         before the ETag) if found, <strong>null</strong> otherwise.
	 */
	Mark skipUntilETag(String tag) throws JasperException {
		Mark ret = skipUntil("</" + tag);
		if (ret != null) {
			skipSpaces();
			if (nextChar() != '>')
				ret = null;
		}
		return ret;
	}

	final boolean isSpace() throws JasperException {
		// Note: If this logic changes, also update Node.TemplateText.rtrim()
		return peekChar() <= ' ';
	}

	/**
	 * Parse a space delimited token. If quoted the token will consume all
	 * characters up to a matching quote, otherwise, it consumes up to the first
	 * delimiter character.
	 * 
	 * @param quoted
	 *            If <strong>true</strong> accept quoted strings.
	 */
	String parseToken(boolean quoted) throws JasperException {
		StringBuffer stringBuffer = new StringBuffer();
		skipSpaces();
		stringBuffer.setLength(0);

		if (!hasMoreInput()) {
			return "";
		}

		int ch = peekChar();

		if (quoted) {
			if (ch == '"' || ch == '\'') {

				char endQuote = ch == '"' ? '"' : '\'';
				// Consume the open quote:
				ch = nextChar();
				for (ch = nextChar(); ch != -1 && ch != endQuote; ch = nextChar()) {
					if (ch == '\\')
						ch = nextChar();
					stringBuffer.append((char) ch);
				}
				// Check end of quote, skip closing quote:
				if (ch == -1) {
					err.jspError(mark(), "jsp.error.quotes.unterminated");
				}
			} else {
				err.jspError(mark(), "jsp.error.attr.quoted");
			}
		} else {
			if (!isDelimiter()) {
				// Read value until delimiter is found:
				do {
					ch = nextChar();
					// Take care of the quoting here.
					if (ch == '\\') {
						if (peekChar() == '"' || peekChar() == '\''
								|| peekChar() == '>' || peekChar() == '%')
							ch = nextChar();
					}
					stringBuffer.append((char) ch);
				} while (!isDelimiter());
			}
		}

		return stringBuffer.toString();
	}

	void setSingleFile(boolean val) {
		singleFile = val;
	}

	/**
	 * Gets the URL for the given path name.
	 * 
	 * @param path
	 *            Path name
	 * 
	 * @return URL for the given path name.
	 * 
	 * @exception MalformedURLException
	 *                if the path name is not given in the correct form
	 */
	URL getResource(String path) throws MalformedURLException {
		return context.getResource(path);
	}

	/**
	 * Parse utils - Is current character a token delimiter ? Delimiters are
	 * currently defined to be =, &gt;, &lt;, ", and ' or any any space
	 * character as defined by <code>isSpace</code>.
	 * 
	 * @return A boolean.
	 */
	private boolean isDelimiter() throws JasperException {
		if (!isSpace()) {
			int ch = peekChar();
			// Look for a single-char work delimiter:
			if (ch == '=' || ch == '>' || ch == '"' || ch == '\'' || ch == '/') {
				return true;
			}
			// Look for an end-of-comment or end-of-tag:
			if (ch == '-') {
				Mark mark = mark();
				if (((ch = nextChar()) == '>')
						|| ((ch == '-') && (nextChar() == '>'))) {
					reset(mark);
					return true;
				} else {
					reset(mark);
					return false;
				}
			}
			return false;
		} else {
			return true;
		}
	}

	/**
	 * Register a new source file. This method is used to implement file
	 * inclusion. Each included file gets a unique identifier (which is the
	 * index in the array of source files).
	 * 
	 * @return The index of the now registered file.
	 */
	private int registerSourceFile(final String file) {
		if (sourceFiles.contains(file)) {
			return -1;
		}

		sourceFiles.add(file);
		this.size++;

		return sourceFiles.size() - 1;
	}

	/**
	 * Unregister the source file. This method is used to implement file
	 * inclusion. Each included file gets a uniq identifier (which is the index
	 * in the array of source files).
	 * 
	 * @return The index of the now registered file.
	 */
	private int unregisterSourceFile(final String file) {
		if (!sourceFiles.contains(file)) {
			return -1;
		}

		sourceFiles.remove(file);
		this.size--;
		return sourceFiles.size() - 1;
	}

	/**
	 * Push a file (and its associated Stream) on the file stack. THe current
	 * position in the current file is remembered.
	 */
	private void pushFile(String file, String encoding, InputStreamReader reader)
			throws JasperException, FileNotFoundException {

		// Register the file
		String longName = file;

		int fileid = registerSourceFile(longName);

		if (fileid == -1) {
			// Bugzilla 37407:
			// http://issues.apache.org/bugzilla/show_bug.cgi?id=37407
			if (reader != null) {
				try {
					reader.close();
				} catch (Exception any) {
					if (log.isDebugEnabled()) {
						log.debug("Exception closing reader: ", any);
					}
				}
			}

			err.jspError("jsp.error.file.already.registered", file);
		}

		currFileId = fileid;

		try {
			CharArrayWriter caw = new CharArrayWriter();
			char buf[] = new char[1024];
			for (int i = 0; (i = reader.read(buf)) != -1;)
				caw.write(buf, 0, i);
			caw.close();
			if (current == null) {
				current = new Mark(this, caw.toCharArray(), fileid,
						getFile(fileid), master, encoding);
			} else {
				current.pushStream(caw.toCharArray(), fileid, getFile(fileid),
						longName, encoding);
			}
		} catch (Throwable ex) {
			log.error("Exception parsing file ", ex);
			// Pop state being constructed:
			popFile();
			err.jspError("jsp.error.file.cannot.read", file);
		} finally {
			if (reader != null) {
				try {
					reader.close();
				} catch (Exception any) {
					if (log.isDebugEnabled()) {
						log.debug("Exception closing reader: ", any);
					}
				}
			}
		}
	}

	/**
	 * Pop a file from the file stack. The field "current" is retored to the
	 * value to point to the previous files, if any, and is set to null
	 * otherwise.
	 * 
	 * @return true is there is a previous file on the stack. false otherwise.
	 */
	private boolean popFile() throws JasperException {

		// Is stack created ? (will happen if the Jsp file we're looking at is
		// missing.
		if (current == null || currFileId < 0) {
			return false;
		}

		// Restore parser state:
		String fName = getFile(currFileId);
		currFileId = unregisterSourceFile(fName);
		if (currFileId < -1) {
			err.jspError("jsp.error.file.not.registered", fName);
		}

		Mark previous = current.popStream();
		if (previous != null) {
			master = current.baseDir;
			current = previous;
			return true;
		}
		// Note that although the current file is undefined here, "current"
		// is not set to null just for convience, for it maybe used to
		// set the current (undefined) position.
		return false;
	}
}
